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Adding Water to Batteries

What is the general rule of thumb? I once read about when to add water to batteries - something about either before or after the charging process. I can't remember what the rule was. Anyone recall when the "right" time is to water the batteries as it relates to the charging cycle. For example, is it better to water after the batteries have experienced a draw such as being on the hook all weekend, or is it better to water them before we leave the dock when they are fully charged? Or, does it really not matter in our boats?

Re: Adding Water to Batteries

Originally Posted by SKYCHENEY

Equalization charge which raises the voltage for a short time to descale the plates.

???????...OK...can you put that in "blonde" terms? I still don't understand...but then again, as Pascal can attest...I'm electrically challenged when it comes to DC systems. Pascal can also tell you...when he tries to explain DC stuff to me, my eyes just glaze over, and then he gives up, but there is hope...I used to be like that for many, many years with football - I was in my mid 30s before I "got it", and look at the college football junkie I am now!! LOL

Is there something I'm supposed to be doing every so often as MikeP mentioned, which I'm probably not doing? I feel like I'm missing something, here.

Re: Adding Water to Batteries

When the battery is working, little bits of stuff (scale) collect on the plates as DC power is used.

After a while, enough stuff has collected on the plates that the battery can not produce power.

When you charge the battery, it reverses the process and the stuff sheds off the plates. Charging the battery also causes the liquid to bubble a bit and if left unchecked, this could lower the liquid level to the point the plates are exposed which will damage them. So the answer to your first question is to top off batteries BEFORE charging.

Most chargers today are smart in that they will adjust the charge rate proportional to how much the battery needs. You can leave a smart charger on for extended time. (I always turn off the charger before starting the engines to avoid a power surge)

The equalization charge is a low power charge designed to keep the plates scale free and batteries in peak condition.

So, go to Walmart and pick up a gallon of distilled water to keep in the ER. Use this to top off the battery banks every 2-4 weeks.

Re: Adding Water to Batteries

Adding distilled water periodically and NEVER letting plate tops become exposed is appropriate. Keep in mind that when you add water the electrolyte solution will have an uneven mixture...water on top and electrolyte below....so in general adding water before or during charging when dockside is a good time because the charging bubbles will help mix the electrolyte solution.

Equalizing depends on how much the batteries are used. If you deep cycle batteries continuously as when cruising and hanging on the hook, more frequent equalization is recommended. But I was never able to get any rules of thumb from several battery manufacturers....but charger makers provide that capability so either it's a real benefit or a marketing/ competitive gimmick...I still don't know which.

I do know that spring and fall equalizing of my 8D's, usually for about 8 to 12 hours, with six mos full time cruising and cycling from May thru October and mostly winter idle time during the cold weather did NOT make any discernable difference in battery life. I got about five years before the twice annual equalization and the same after...consistently one cell or ocassionaly two would become weak within a battery or two and that's when I had to replace the bank....several times if one battery cell became virtually weak or dead and I replaced that battery alone, then the other batteries of equal age and use would fail within six mos or less....so I developed the preventative measure of changing all batts in a bank when one failed at at about five years. I still don't know why one cell fails so often before others.

I used Power Master, Exide, and Interstate 12v Deep Cycle with about equal results as far as I could tell. Usually as charge time to get to about 85% of full charge during cruising became longer, I'd check and find that bank at 4 to five years of age and consistently during the following winter a cell or two would weaken and I'd replace the bank the following spring before departure. I rotated 3 bank replacement times so I always had one bank aboard that was only one or two years old.

Last edited by REBrueckner; 09-25-2010 at 03:12 PM.

Rob Brueckner
former 1972 48ft YF, 'Lazy Days'
Boating isn't a matter of life and death: it's more important than that.

Re: Adding Water to Batteries

i dont think your charger has an equalization mode... otherwise one a year is usually fine. you need to check water before and after and make sure it's all well ventilated (caps and battery box covers off)

i really dont' think when you top off the batteries matter, at least out in the real world. I'm sure someone will find a white paper somewhere which will argue why one way of another is best...